Biological molecules

What are the 3 biological molecules?

Carbohydrates

Proteins

Lipids

What elements do carbohydrate contain?

Carbon (C)

Hydrogen (H)

Oxygen (O)

Carbohydrates are made up of…

Simple sugars

What is a monosaccharide?

1 simple sugar unit

(e.g. glucose & fructose)

What is a disaccharide?

2 simple sugar units bonded together

(e.g. sucrose, lactose & maltose)

What is a polysaccharide?

Multiple simple sugar units bonded together

(e.g. starch, cellulose & glycogen)

Carbohydrates are used to…

Provide energy for all life processes

What elements do protein contain?

Carbon (C)

Hydrogen (H)

Oxygen (O)

Nitrogen (N)

Proteins are made up of…

Chains of amino acids

Protein is used for…

- Growth & repair

- Production of enzymes, haemoglobin, hormones & antibodies

- Some are also used structurally for hair & nails

What elements do lipids contain?

Carbon (C)

Hydrogen (H)

Oxygen (O)

Lipids are made up of…

3 fatty acids & glycerol

Lipids are used for…

- Long-term energy store

- Insulation

- Protection of organs

Food test for starch (method)

1. Prepare a starch food sample & transfer it onto a white spotting tile or test tube

2. Add of few drops of iodine solution to the food sample

Food test for starch (results)

Positive → solution will turn blue / black

Negative → solution will remain yellow / brown

Food test for protein (method)

1. Prepare a protein food sample & transfer it onto a white spotting tile or test tube

2. Add 1cm³ of Biuret solution to the food sample

Food test for protein (results)

Positive → solution will turn lilac / purple

Negative → solution will remain blue

Food test for sugar (method)

1. In a test tube, add equal quantities of simple sugar food sample & Benedict’s solution

2. Boil the test tube in a water bath heated at 95ºC & leave for 5 minutes

Food test for sugar (results)

Positive high concentration → solution will turn into a brick-red precipitate

Positive low concentration → solution will turn yellow or green

Negative → solution will remain blue

Food test for lipids (method)

1. Prepare a lipid food sample in a test tube & add 4cm³ of of Ethanol to it

2. Gently shake well & then leave for 1 minute

3. Carefully remove the layer of fat that has formed at the top of the solution & add it to a test tube of water

Food test for lipids (results)

Positive → solution will turn into a cloudy white emulsion

Negative → solution will remain colourless